1. Field of the Invention
This invention relates to an illumination light application structure for irradiating an observation object with illumination light in an observation optical apparatus provided with an objective lens inside a lens barrel whose top is configured into a slender shape, and to an endoscope provided with this illumination light application structure.
2. Description of Related Art
Endoscopes have been used for observations of parts in which observations from the exterior are difficult, such as internal therapies and/or diagnoses of patients in a medical field and internal inspections of holes provided in products in an industrial field.
In general, the endoscope has an objective optical system and an image transmitting optical system such as a relay lens (in the case of a rigid scope) and an image guide fiber (in the case of a flexible scope) inside a tubular insertion section of tiny diameter at the distal end. The endoscope is thus constructed so that light passing through these optical systems from an observation object is observed as an observation image through an ocular optical system and an imaging optical system. A video endoscope is designed to house the objective optical system and an image sensor, such as a CCD, in the distal end.
In the endoscope, an illumination means for illuminating the observation object observed through the objective optical system is placed on an optical path different from that of the objective optical system. The structures of the illumination means in such endoscopes are set forth, for example, in Japanese Patent Kokai Nos. Hei 10-216085 and Hei 4-244130. The illumination means of the endoscope set forth in Kokai No. 10-216085, for example, as shown in FIG. 1, is constructed so that, at a distal end 50 of the endoscope, a plurality of LEDs 52a and 52b are arranged around or on the side of an observation system 51 and the observation object is irradiated with illumination light from the plurality of LEDs 52a and 52b. On the other hand, the illumination means of the endoscope set forth in Kokai No. 4-244130, for example, as shown in FIG. 2, is constructed so that a light guide 62 is provided in an annular shape around an observation system 61 at a distal end 60 of the endoscope.